The present invention relates to packingless gate valves and more particularly to gate valves having a specific construction of internal components including elastomer sleeves and a secondary seal which result in improved operation in sealing of the gate. The valves of the present invention are capable of use as knife gate valves and may be used for any of various fluid or dry powder control operations. The gate valves of this invention are particularly well suited for use with abrasive and corrosive slurries.
The present invention is an improvement of the gate valves as described in previous Clarkson patents, including U.S. Pat. Nos. 3,945,604; 4,007,911; 4,257,447; 4,895,181; and 5,271,426.
In accordance with the present invention, an improved construction is provided as compared to the gate valves of previous patents by a special arrangement of a clean out area and also by the use of a secondary seal structure within the valve housing. The secondary seal has a novel coaction with the gate and is mounted in a novel manner in the valve housing.
The present invention employs a valve construction which is based on the resilient seating of elastomer sleeves against a sliding gate. As the gate slides between a pair of primary sealing sleeves during the valve opening or closing operation, the opposing primary sleeves are caused to move axially, coming together and separating respectively. The secondary seal, positioned externally of the primary sleeves, also engages the gate during the valve cycle and acts to prevent any discharge which may seep through the primary sleeves from leaking to the atmosphere around the gate or on the actuator end of the valve. Additionally, an enlarged clean out area is cast into the housing to collect slurry discharge to be flushed out of the valve housing through exit ports in the valve body regardless of the valves installed position.
Accordingly, it is an object of the present invention to provide a novel gate valve assembly wherein a resilient secondary seal unit is mounted in a special manner in the valve housing and has special coaction with the relatively slidable gate, with the secondary seal acting to prevent any slurry discharge from leaking to atmosphere around the gate or on the actuator end of the valve.
A further object of the invention is to provide a novel gate valve assembly wherein the housing is provided with an enlarged clean out area and flush ports to facilitate collection and removal of slurry discharge during an actuating cycle.
Further objects of the invention will be apparent from the following description as taken with the appended claims and the accompanying drawings.